Even if we had
ISP supporting caches, there is always the problem getting p2p clients
to support them (given they often are too busy trying to circumvent).
I fail to see the point. If an ISP needs to add caches they may
as well just add a simple, cheaper, standard, http cache.
No special clients required, no fiddling to make locality work
and no extra, expensive in some architectures, last mile traffic
It's a bang-per-buck issue, and depends highly on whether your
particular network sees more HTTP or P2P traffic. If HTTP is 60%
of your traffic, an http cache makes sense. If P2P is 70% and
HTTP is 20%, it probably doesn't make sense.
And the only numbers that matter here are what *you* measure
at the point you intend to install the cache - I've seen so many
conflicting numbers for different parts of the net that no firm
conclusions can be drawn.